Accurate determination of a quantity of a fluid inside a tank can be difficult. For example, certain methods of estimating an amount of a liquid propellant that remains in a satellite's fuel tank may not have a desired accuracy. When mission planners do not know with a high degree of confidence how much fuel is left in the satellite's fuel tank, the satellite may be retired prematurely, which may be wasteful of the remaining fuel and of remaining useful life of the satellite.